Effects of substrate temperature and oxygen pressure in pulsed laser deposited ZrW1.5Mo0.5O8 thin films

Abstract ZrW 1.5 Mo 0.5 O 8 thin films were deposited on quartz substrates by a pulsed laser deposition (PLD) method at various temperatures from room temperature to 500 °C and different oxygen pressures from 5 Pa to 20 Pa. The effects of substrate temperature, ambient O 2 pressure on the phase composition, growth and surface morphology of the ZrW 1.5 Mo 0.5 O 8 thin films were investigated using the X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The negative thermal expansion property and phase transition in cubic ZrW 1.5 Mo 0.5 O 8 thin film were characterized using high temperature X-ray diffraction (HTXRD). The XRD studies indicated that the as-deposited ZrW 1.5 Mo 0.5 O 8 thin films showed amorphous phase regardless of O 2 pressures and substrate temperatures. Crystallized cubic ZrW 1.5 Mo 0.5 O 8 thin film was prepared after annealing at 1180 °C for 7 min. The AFM studies showed that the root mean square (RMS) roughness values of the ZrW 1.5 Mo 0.5 O 8 thin films decreased from 13.557 nm to 4.184 nm. This corresponded with increasing substrate temperature from room temperature to 500 °C. The RMS roughness values increased from 2.526 nm to 7.231 nm with increasing O 2 pressures from 5 Pa to 20 Pa. The HTXRD analyses demonstrated that the cubic ZrW 1.5 Mo 0.5 O 8 thin film exhibited strong negative thermal expansion and its average thermal expansion coefficient was calculated to be −7.7×10 −6 K −1 in the temperature range from 30 °C to 600 °C.